Technical should I use a relay for fuel pump?

[bobscogin]

Originally Posted by Truckedup

or a dash push button to prime the carb before starting...

Primer button works well. I used one on my T roadster, but not in the dash. It's hidden.

Bob

[harley rider]

hey thanks every one.I will use a relay on the pump and fan.I found some more wire diagrahms wich one of these is correct or is the87 and 30 terminal in or out?

[cherokee_64]

Here you go, read this:

http://www.how-to-build-hotrods.com/...fuel-pump.html

It has all the info on how to do your electric fuel pump the right way, what kills electric fuel pumps, and diagrams on wiring it up...

[jack orchard]

i like the oil pressure switch cutoff idea with a primer button. never would have thought of this. thanks to everyone...jack

[mustang6147]

I hate inertia switches. I hate complicated things as well.

Relays are a great idea. The relay simply is an electric switch. So you have the power wire going to the relay then out to the pump. You have a thinner wire that activates the relay. The purpose of this, is to reduce switch failure, on longer runs of wire. My biggest reason is, its a pain the a$$ having thicker wire connected to a switch, Thinner is neater, and out of the way, this also adds to safety. So its a win win.

[harley rider]

Originally Posted by cherokee_64

Here you go, read this:

http://www.how-to-build-hotrods.com/...fuel-pump.html

It has all the info on how to do your electric fuel pump the right way, what kills electric fuel pumps, and diagrams on wiring it up...

Thanks cherokee that was helpful

[A Rodder]

30 is power in
85 is ground
86 is switched power in
The 87 pins are power out

I also believe 85 and 86 can be swapped with no effects.

[A Rodder]

Remember to put your fuse as close to the battery as possible.

[1950coronet600hp]

my rule of thumb is to put anything of somewhat heavy amp draw on a relay.. it takes the amperage off the switch, which is a good thing. and seeing relays are about 7 bucks it should be a no brainer...

[tommy]

The first 55 years of my hotrod life we never used a relay. The last ten there has been a big change on the internet anyway. To me a relay is just something else that can break and leave you on the side of the road. Of course I'm talking about the old Dupree/ SW style and other electric pumps for carbs. I always wire it through the key switch so I don't forget to flip the switch. I just turn the key to "on" and listen until clicking slows down, pump the gas twice and start it up. I believe in the KISS system. The less parts to break....the better. JMO

[26 roadster]

yea tommy I did it the same way as you but now I run relays on everything and think it is better. That could by oldtimers though!!!!!!!!

[harley rider]

Originally Posted by A Rodder

30 is power in
85 is ground
86 is switched power in
The 87 pins are power out

I also believe 85 and 86 can be swapped with no effects.

why is it I see diagrahms with 30 out and 87in?

[40FordGuy]

Relays, Always !!

[c-10 simplex]

Originally Posted by squirrel

The "red fuel pump power wire" is what you connect to the switch, whether it's the ignition switch directly, the oil pressure switch, or the toggle switch.

Does it matter if the fuse is in between the batt and relay or in between pump and relay and why?

P.S. i still don't fully understand relays, because there is still small gauge wire running to and from the relay---i thought the reasons for relays is to be able to handle high amp loads without overtaxing switches and smaller gauge wiring?

[EXracer64]

The point is to avoid voltage drops across the switch, and the arcing that occurs on a switch when its "switched". The smaller guage wire is to actuate the relay/switch and complete the circuit on the larger guage wire. The relay is only breaking one side of the feed voltage.

[langy]

Think of your starter solenoid as a relay, you wouldn't want a huge switch on the dash.

It's basically just a remote switch with heavy duty terminals to pass large current a small switch couldn't handle.

Most quality relays have the circuit diagram on them so it's easy to understand.


Sent from my iPhone using TJJ app

[31Vicky with a hemi]

Originally Posted by c-10 simplex

Does it matter if the fuse is in between the batt and relay or in between pump and relay and why?

P.S. i still don't fully understand relays, because there is still small gauge wire running to and from the relay---i thought the reasons for relays is to be able to handle high amp loads without overtaxing switches and smaller gauge wiring?

Yes it matters.
Because the relay is also protected.

The light gauge wires control the relay.
A relay is an electromagnetic contactor (electric switch) that can be controlled with very little amps and a very light duty switch. The relay can control very high amperage load.

[c-10 simplex]

What size wires would go to 30 and 78 in the fuel pump diagram?


b) What about for an electric fan?

[outlaw256]

Originally Posted by tommy

The first 55 years of my hotrod life we never used a relay. The last ten there has been a big change on the internet anyway. To me a relay is just something else that can break and leave you on the side of the road. Of course I'm talking about the old Dupree/ SW style and other electric pumps for carbs. I always wire it through the key switch so I don't forget to flip the switch. I just turn the key to "on" and listen until clicking slows down, pump the gas twice and start it up. I believe in the KISS system. The less parts to break....the better. JMO

same here tommy.i dont use a relay on my fuel pumps ign. box etc. about the only thing i use them on is headlites and starters if need be.more elecrical=more problems.but i run my fuel pumps on a BIG toggle switch and a fuse.thats all.done it that way for 40 yrs now. never lost a pump or had a fire.

[FOURTYDLX]

Go to salvage yard,roll over switch in big fords is located in trunk lft side behind card board. they work great>